1. Field of the Invention
The present invention relates to a bicycle with an auxiliary power unit capable of regenerating electric energy by using a rotational force of a wheel.
2. Description of Background Art
A known power-assisted bicycle, such as a bicycle with an auxiliary power unit, uses a motor as a regenerative power generator during, for example, deceleration to thereby recover kinetic energy as electric energy.
Japanese Patent Laid-Open No. 2001-114179 discloses a kinetic energy regenerative apparatus for a motor-driven bicycle. The kinetic energy regenerative apparatus generally includes a first driving force transmitting element, a second driving force transmitting element, an idler sprocket, and a driving force connecting/disconnecting clutch. More specifically, the first driving force transmitting element is fixed to a rear wheel hub and rotated with the rear wheel hub during regeneration. The second driving force transmitting element is driven by rotation of the first driving force transmitting element. The idler sprocket is driven by rotation of the second driving force transmitting element and meshes with a chain. The driving force connecting/disconnecting clutch is interposed between the chain and the motor. The arrangement allows the first driving force transmitting element, the second driving force transmitting element, and the idler sprocket to transmit rotation of the rear wheel hub to the chain during regeneration and the driving force connecting/disconnecting clutch to transmit rotation of the chain to the motor. As a result, electric energy can be regenerated using the rotational force of the wheel.
Japanese Patent No. 4036776 discloses an electric power-assisted bicycle that can regenerate electric energy with a simple structure in which a clutch unit that is operatively associated with a braking operation performed by a rider to change locking directions is connected to an output shaft of a motor.
However, the arrangement disclosed in Japanese Patent Laid-Open No. 2001-114179, includes the driving force connecting/disconnecting clutch for regeneration, the first driving force transmitting element, and the second driving force transmitting element, which contributes to a complicated structure and increased cost. Further, during deceleration, the rotational force of the wheel is converted to corresponding electric energy at all times, leaving the user no option of selecting whether or not to regenerate the electric energy.
In the related art disclosed in Japanese Patent No. 4036776, the locking directions are changed only when the rider performs the braking operation, so that the electric energy cannot be regenerated without the braking operation.